Need help with this!!

Determine whether the set of whole numbers is closed under addition. explain why the set is or is not closed. give an example.

Rena is building a 1: 180 scale model of a real castle. her model has a rectangular base that is 3 feet wide and 4 feet long what is the area of the base of the actual castle in square feet

What is the effect on the graph of the function f(x)=x when f(x) is replaced with -f(x)+4